The 4% is cheating and should be banned

How do you police the shoes at a road race if most of the top athletes are actually wearing prototypes? You would need an x-ray machine.

... And no, not the Zoom Flys but yes the new Zoom Fly Flyknits.

Try concentrating on understanding why exactly there's a difference between a carbon fiber and a nylon plate then you should be able to work out why this should be for yourself!

T Funke wrote:

The comments on here as to it's spring mechanism all seem to make sense (and these diagrams looked at together certainly visualise what's going on) but as to the OP's question should they really be banned?

Has not this technology been around before? About 15 years ago Adidas had their pro-plate technology which was a carbon fiber plate in their racing flats (adistar comp?) and back in the mid 1990s Fila had their Silva racer which had a carbon fiber plate as well. What is the actual difference between these shoes and the newer Nike 4% racing flat?

Has anyone tried the 4% on grass or trails? Same benefit? (Granted there isn't much traction on them.)

The “magic” in that shoe is indeed the PeBax foam, for two interacting reasons:

1 - It has substantially greater energy return than any other midsole material. The streak “returned” 66% of energy, the adios boost 76%, and the VaporFly 87%. That means almost 1/3 more of the mechanical energy from each footfall is preserved rather than being lost to heat

2 - It has approximately HALF the density of EVA. That means for the same amount midsole foam, it weighs half as much, which thus *costs* less energy to carry. This is why they’re able to put so much foam on there - its double the “cushioning” material at the same weight.

So, you now have a midsole that both returns more energy and costs less energy - proverbially having your cake and eating it too.

The carbon fiber does serve a crucial purpose though - that wonderful foam is a structural nightmare on its own. It would not hold up as singular midsole, and its energy return likely wouldn’t be realized, as the foot would be way too unstable on each footfall. The CF plate thus serves as the lightest possible structural unit for that foam to give it coordinated structure. The shape and its curvature may provide some additional small benefit for some people whose foot interacts with it perfectly, but I suspect the geometries would have to be personally tailored for that to be a true enhancement for the masses.

I suspect Nike is perfectly happy to let everyone think it’s the “crazy” carbon fiber integration that really does wonders, while letting the foam go unheralded, considering its not proprietary. PeBax, while likely pretty expensive to manufacture as a foam instead of a plastic, is not their own tech. In fact, Reebok’s new running shoes incorporate it as a foam.

So, you can think of the foam in the VaporFly as the Kurt Cobain of the shoe, while the carbon fiber is the Dave Grohl.

With respect to regulations, my contention would be that you regulate STACK HEIGHT alone. All shoes are essentially springs, and the VaporFly is just a lot closer to an ideal spring than other shoes. Because of the lighter foam with greater energy return, they can jack the shoe up to a whopping 39mm stack height, essentially adding nearly 2cm to the runner’s leg length as a near-perfect spring.

Companies should be encouraged to get as close as they can to 100% energy return, but it would be pitiful to see it devolve to higher and higher stack heights, essentially driving longer and longer springs (think of pisotrius’s blades as 500 mm springs).

I tweeted this awhile back when Alex Hutchinson, Ross Tucker, and Peter Weyand were chattering about it on Twitter:

https://twitter.com/geoffreyburns/status/1046867598758031361

there are other shoes that use pebax but do not have the performance of the spring in vaporflys (oncloud and reebok maybe others)

also the newer model of the zoomflys uses carbonfiber, nylon is old model

again, Nike makes a pebax-only version, no-one uses it for good reason, but it would be simple to compare the two

so the answer is simple, IAAF/USATF need to commission their own study and then implement a ban on leaf-springs in shoes based on the results which will be obvious

but they haven't even moved to do a study which really is casting a shadow on their independence to all the money they/their voters take from the industry

Yes. Exactly. Agree with everything you said 100%.

zoomzoomzoom wrote:

so the answer is simple, IAAF/USATF need to commission their own study and then implement a ban on leaf-springs in shoes based on the results which will be obvious

A leaf-spring works because the spring eyes are fixed. Same thing with a diving board; it has to be bolted down to the deck of the pool in order to flex when you jump on it.To get spring out of a carbon plate when you jump on it you'd have to have a plate that extends way beyond your foot and is fixed at both ends. You could also have something with a sideways U-shape, like a prosthetic running leg. But a flat "leaf spring" that matches the shape of your foot is not going to be "springing" you at all. It's be like setting a diving board down on a flat concrete floor and jumping on it.

Your diving board on a flat concrete floor analogy is garbage. Actually look at how the carbon plate is angled. Then consider the foam cushioning beneath that. Then try to think why these shoes have such a limited shelf life. What do you think begins to happen to the carbon plate as that foam begins to lose its shape?

https://m.imgur.com/VfRS4sM?r

This article is exactly right. Take out the carbon fiber spring from this shoe and I have no problem with it.

https://sportsscientists.com/2017/03/ban-nike-vaporfly-carbon-fiber-devices-future-performance-credibility/

You really are one of the stupidest people I’ve ever read a post from or encountered.

It’s very simple. Let me lay this out very easy so your tiny brain can understand.

THEY BOTH HAVE A PLATE IN THEM!

This is why I’m asking the same question and still failed to get a response from anyone.

You only want to blame plates made up of certain materials? What materials? Can it be a percentage of carbon and nylon? Where exactly are you drawing the line? This is how rules work if you want to ban a shoe.

Tell me exactly what it is about the shoe you want to ban.

“It has a spring.” So does the ZF! Do you want to ban that as well or only certain types of “springs”? Please tell me which types and materials, otherwise none of you have a solid case for an argument.

Do you have to start the same thread every 2 weeks?

You are dumb wrote:

This is why I’m asking the same question and still failed to get a response from anyone...

I answered your question, read the whole thread.

Only 4% think u r intelligent wrote:

Do you have to start the same thread every 2 weeks?

I've never started a thread on this topic at all.

I may be stupid I guess but I should be happy not to be so stupid as to link to a site which disproved exactly what I was arguing in the first place ?

Plus, you've also managed to ignore the fact that I already replied subsequently, and very specifically, re the rest of your post. But once again you've obviously too busy frothing at the mouth to actually carefully read what's even written in this thread...

It's the carbon fiber plate that people take issue with, no one gives a flying f*ck about nylon!! Do you really not comprehend the difference in their structures? You realize the

complete difference in terms of rigidity we're talking here? (I'm not sure you do otherwise you wouldn't be posting such drivel)

Here you go (again!). How could you possibly have read this and then wrote a big rambling post re what about the shoe should be banned?!!

No point made other than you are an utter Cretin wrote:

... And no, not the Zoom Flys but yes the new Zoom Fly Flyknits.

Try concentrating on understanding why exactly there's a difference between a carbon fiber and a nylon plate then you should be able to work out why this should be for yourself!

RuppSertified wrote:

Vaporfly Asterisk wrote:

mmm, I suspect you really know the answer already but playing devil's advocate let's have a look at this picture:-

https://thingiverse-production-new.s3.amazonaws.com/assets/00/b9/14/0a/12/Class_lever_1.gif

Now what's the major difference as far is this goes between Vaporflys and spikes?

Clue: It's the reason Vaporflys are essential f*cked after ~ 100 miles.

That diagram shows you how to fuk both your PF and your achilles!!

Some gems in here, besides the tool who keeps whining about springs.

Only 4% think u r intelligent wrote:

Do you have to start the same thread every 2 weeks?

That handle wins the thread :)

do your researchh wrote:

It's not the foam, it's THE CARBON FIBRE PROSTHETIC LIMB that is hidden inside the shoe that works like Oscar Pistorious's legs except on a smaller scale.

Nicely put. Not sure if everyone on here make daft comments re the foam being some sort of Mac & Jack's Wonder Potion really understand that there's such a solid, rigid material in there - literally a hidden spring.